After many years of resistance, I have at last signed up for WhatsApp, and I have to say it's all I thought it was going to be: a half-baked solution that has captured so many people who don't (yet1) appreciate what they've opened themselves to.
The installation process was straight-forward enough. You download the app onto your 'phone and you tell it your 'phone number, and bang, you're ready to go.
Except you're not.
Uploading 'phone's contact details
The first problem I encountered was that WhatsApp would not work for me until I agreed to upload my 'phone's contacts.
I understand there are reasons for allowing WhatsApp to read your 'phone's contacts, among them being that it's easier to send messages to the people you know. However, allowing it to do so comes with an unintended consequence (or, perhaps intended from WhatsApp's perspective!): WhatsApp gets to take a copy of all the 'phone numbers in my 'phone's contacts even if some, or just one, of the people whose numbers they are don't want me to share this detail with WhatsApp.
None of the "… but it makes things so easy for you" arguments, or the "… they store it in a non-identifying manner" explanations address the violation of privacy of the person whose number it is.
Similarly, the answers to the questions "Who in your contacts, anyway, wouldn't want you to contact them over WhatsApp if they're already on it?" and "Why would someone not want you to share their number?" don't matter.
If there's 1 person (of the ~200 in my contacts) who doesn't want their number copied from my 'phone to WhatsApp's servers, then I have a responsibility to respect that in the same way as I have a responsibility to respect a sign that says "No junk mail" or "Stay off the lawn".
Broadcasting to all I'm here
If I, who resist this sort of thing as a habit, can't figure out how to use WhatsApp without uploading all my 'phone's contacts, I can only guess that all other WhatsApp users have also uploaded their contacts to the servers. Including those who were keeping my number in their contacts!
So, now those people know that I am on WhatsApp, even if I don't want them to. I don't understand why I can't control who can know I'm on WhatsApp and who shouldn't.
I would bet that there is a significant abuse problem on WhatsApp. Trolls, and abusive ex-s, and nasty supporters of nasty political parties can all see if those they want to target are on WhatsApp: all any of them needs to do is create a contact with their target's 'phone number, and they can see that they're there, at least (I guess) until they are blocked. This puts the onus on the innocent party to manage these people, to protect themselves against abuse or threatened violence, and only after the nastiness has commenced. That shouldn't be necessary; we should be allowed to keep our presence on WhatsApp private, with only those we want to be in contact with knowing.
Tying my WhatsApp account to my 'phone number?! Are you completely out of your mind?!?!?
I operate many e-mail addresses, and each one has a specific purpose. When I send an e-mail from one account, it's in part because I want the recipient to interact with me only over that address, and not any of the others. None of my e-mail addresses are tied to any other means of contacting me, including my 'phone number, and this is good.
Similarly, just because someone knows how to send a DM to me in twitter, it doesn't follow that they should know what my 'phone number or e-mail address are.
There is literally no good reason I can think of that benefits me to tie my WhatsApp account to my 'phone number. Signal does this too, and it's stupid, put simply.
My 'phone number is part of my identity, just like my home address, my mother's maiden name and my PPSN3. When I give my 'phone number to someone else, I open up a small new vulnerability in my personal security: I am allowing the recipient to make contact with me, and I depend on their good faith not to do so inappropriately. If that vulnerability gets exploited in a distressing way, I would have to consider taking the drastic measure of changing my 'phone number, of erasing 23 years of part of my identity.
I would be very surprised to learn that no one in the world has had to change their number because someone on WhatsApp abused that access. In fact, I would be very surprised to learn it's not a common event.
When I first got a personal 'phone number (in 1998), I opted not to have it listed in the telephone directory. This was in part because my (family's) home 'phone number had been ex-directory since the early 1980s. It made sense. It still does. Now that I am on WhatsApp, those nearly 40 years of a simple protection measure have been flushed down the drain, simply because it "makes it soooo much easier for people to get in touch with" me.